<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1{
            width: 200px;
            height: 200px;
            background: pink;
            /* padding: 0px;
            border: 0; */
            overflow: hidden;
        }
        .box2{
            width: 100px;
            height: 100px;
            background: blue;
            margin-top: 50px;
        }
    </style>
</head>
<body>
    <div class="box1">
        <div class="box2"></div>
    </div>
</body>
<script>
function Foo(){
    this.name="test1";
    function bar(){
        this.name="test2"    };
    bar(); 
}  
Foo.name = "test3"; 
var foo = new Foo(); 
</script>
</html>